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13

Yes and in this case this is due to induced drag. This drag can be derived with the lift and drag equations of a wing : $$\textit{Lift} = \frac{1}{2} \rho C_L S V^2$$ $$\textit{Drag} = \frac{1}{2} \rho C_D S V^2$$ With decomposition on first order of the drag coefficient as follow $$C_D = C_{D_0}+k C_L^2$$ We get, $$D = \frac{1}{2} \rho (C_{D_0}+k C_L^2) S V^...


10

When looking at statements like these, it's important to consider which parameters are varied and which parameters remain fixed. Let's get this out of the way first by correcting your statements: Lift increases with increase in airspeed with constant angle of attack but induced drag reduces with increase in airspeed with lift force remaining constant ...


8

While it’s not a true air to air fighter, following are some comparison numbers for the EA-6B Prowler that might help provide a useful ratio for a tactical "fighter type" aircraft. (Information comes from the NATOPS pocket checklist, under the constant altitude “bingo” fuel divert tables.) Theses figures are for a flaps-up aircraft, fully loaded ...


7

Yes, and it occurs with nearly every airplane there is. It is caused by lift-induced drag. Lift is created by a wing deflecting airflow downward, itself being pushed upward as a result. (Newton's third law) Lift-induced drag is the backward component of the resulting reaction force acting on a wing. Since at lower speed, the wing needs to be tilted up more ...


7

In 1961 study a plane flew 116,684 miles sampling the air, catching whatever was up there, and managed to capture a single termite at 19,000 feet. This is the highest ever observed. You just never get above the "bug layer" in a smaller aircraft (Cessna 172 limit is 15,000 feet). Likely this is not a proper naming.


7

They just got this wrong. I have flown F28-1000 and -4000, the F100 and the B767-300. The most feet per nautical mile lost of these with idle power at any given Indicated Air Speed (say 270-280 below 25000 ft) is the F28-1000 (around 475 fpnm) then the F28-4000 at about 425 fpnm, then the F100 at about 350 fpnm and the best is the B767 at about 300-330.The ...


7

Cockpit windows that sit flush with the fuselage can save a very small amount of drag, but they require large double curvature window panes. Manufacturing such panes is significantly more expensive and there was limited commercial availability for that product when the A320 was being designed. You can see a few more examples of flat vs curved windows here: ...


7

Amazing! British pioneer JW Dunne proposed this as a propulsion system around 1901 but Sir Hiram Maxim told him it would not work. (ref. unpublished documents in the Science Museum Archive's Dunne collection). Nine years later Henri Coanda built a ducted "jet" plane on broadly similar principles, which failed miserably (The Wikipedia article is not ...


7

In a way, yes. By using smooth metal surfaces with countersunk rivets, modern aircraft use a surface with low friction already. In the past, wooden structures were varnished to give them a smoother surface. In the second World War, German crews would polish the normally matte paint of some of their airplanes to eke out the maximum in top speed. There have ...


6

A single source, or a source sheet comprised of infinitesimal sources (sinks are just sources with negative strength), produces a velocity field that contains no circulation. Without circulation, it can't possibly generate any lift. The Source Panel Method is just a discretized computational method for source sheet. It, therefore, only produces non-lifting ...


6

Lift increases with increase in airspeed but induced drag reduces with increase in airspeed. If you keep weight ($W$) constant, the total lift ($L$) does not change with change in airspeed ($V$). $L=W$ for quasi-steady flight, right? What is changed is the lift coefficient, $C_L$. As speed increases, $C_L$ decreases. Induced drag coefficient ($C_{D_i}$) is ...


6

Let's imagine 2 theoretical wings, both of which have the same area, but differ in aspect ratio. Then the wing with the higher aspect ratio also has more span. This is what counts. If induced drag depends on the downwash angle, why would a longer wingspan reduce the angle? Because the wider wing will affect more air. Think of the air affected by the wing ...


5

I don't have any scientific data, but in my flying experience, including some time back in the 70s in a Breezy, where, as on a motorcycle, you have to be careful to keep your mouth closed, you don't encounter that many bugs above 1000 ft agl (they are there, but few and far between relatively). Descending in the Breezy in a warm summer late afternoon with a ...


4

Wind tunnels are stingy with the data they reveal. They only give the total value but not neatly split into its contributions. Therefore, any such table needs to be calculated. Since XFOIL, which is now around for more that 30 years, we have such a tool and it does output the single contributions. However, I know of no publicly available collection which ...


4

It's because interference drag (the vertical flow field forced to share space with the horizontal flow field) is minimized when the wing meets the fuselage at a 90 degree angle or more. With a low wing airplane with dihedral, even if the sides of the fuselage are vertical, there is still less than a 90 degree angle due to the dihedral angle. To mitigate the ...


4

Yes. Lift and Drag are both obtained by multiplying the CL & CD by the same factors (1/2 rho V^2 S); the ratio L/D cancels out those factors, leaving CL/CD.


4

My source is STUDIES OF HIGH LIFT/DRAG RATIO HYPERSONIC CONFIGURATIONS by John V. Becker, to be found online here. It is from 1964, so more than 50 years old, but since a lot of research had been performed already before that date, it might still be relevant. In short: It depends. On thickness ratio and Reynolds number, for example, as can be seen in this ...


3

If you want to arrest ascent you put the airbrake behind/below the CG. Keep in mind the rocket will tend to remain flying "nose first", which may affect parachute deployment (from nose) on the way down. Notice the Space X Falcon 9 has theirs near the nose allowing the rocket to descend tail first, and are only deployed once the rocket has coasted ...


3

It's not that simple (even if we consider only aerodynamics and ignore structural and stability issues). In many practical cases, the top wing is as good or even better than mid-wing. The culptit is, of course, interference drag: the drag that appears when we combine two or more bodies, as compared to these bodies isolated in the same stream. Like any other ...


3

There are multiple ways to decompose lift and drag forces, and they are unfortunately not compatible with each other. If you know the flow field (for example because you ran a CFD simulation), then to compute lift and drag, you need to integrate: pressure forces (i.e. local pressure times surface normal, over area) viscous forces (local viscous stress times ...


3

This has mostly been examined for aquatic flow, e.g. with the soft skin of dolphins. Studies were done with test setups because measuring the boundary layer around live dolphins is exceedingly hard. One study compared a rigid cylinder with a soft one of the same dimensions, using a polyurethane coating. Below is a diagram from that study with 3 denoting the ...


3

The results of a trial made on November 21, 1903, do not match the 1999 wind tunnel measurements. The discrepancy is enormous. The Wright brothers and the people at NASA tested very different planes and propellers otherwise the reported experimental data would have matched well. I do not agree the 1999 experiments, on the full size model of the 1903 plane, ...


3

Induced drag $D_i$ is proportional to the square of lift $L$: $$D_i = \frac{2\cdot L^2}{\rho\cdot v^2\cdot\pi\cdot b^2\cdot\epsilon}$$ where $b$ is wingspan, $v$ is flight speed and $\rho$ is air density. $\epsilon$ is an efficiency factor which tends to be between 0.8 and 1. Compared to straight and level flight, induced drag will quadruple when turning at ...


3

The technical report NACA-TR-824 has been digitized. The digitized version includes Cl and Cd for 118 airfoils at 3 Reynolds numbers. To get it, create an account on x-plane.org. (It's been online sporadically elsewhere over the decades, e.g. here. People associated with the digitizing include Gregory Peter, Gregory Siemens, and James Sonnenmeier.) ...


3

You seem to be confusing force (thrust or drag) with energy (under which concept work and power comes). Don't. You'll be spared much grief. Work done is force times distance. $$ W = Fs $$ Power is work done divided by time $$ P = W/t $$ When you double velocity, force quadruples. As does work. $$ W_\text{new} = 4Fs = 4W $$ Time halves as well, with the ...


3

The downwash is about as high as wide, and angled only by a few degrees (more at slow speed). So the longitudinal distance needs to be many times longer than the wing span to make the wings independent. And it would still be less efficient than increasing the span: If you double the span, you will decrease induced drag four times. If you half the lift, you ...


2

Approximately, yes. Both lift and drag depend on the density of air, so in order to generate enough lift at the same angle of attack in thinner air, an aircraft has to fly faster. Thus the same number of air molecules hit the plane every second and the drag is approximately the same. This is a bit of a simplification (especially the bit about drag being ...


2

Could drag in a turn be twice the drag in straight and level flight? Yes, but this will be a rater steep turn. … in a coordinated turn with the same angle of attack at the same airspeed … No, this is impossible. Either angle of attack or speed have to be higher so the higher lift required for turning can be generated. … angle of attack is the same, the ...


2

Generally, you are right. Reducing wing area is reducing overall drag. Within limits. Induced drag depends on speed and span loading. If the reduced wetted surface allows you to fly faster, reduced drag will be lower, leaving more of the power budget to overcome viscous drag. However, if wing span is reduced, induced drag will be higher at the same speed, so ...


2

It's not so simple. For swept wings it is essential whether the leading edge is sub- or supersonic. What does that mean? If the leading edge is within the Mach cone emanating from the tip of the wing, it is called subsonic. The approaching air will "sense" what is coming and behave much like in subsonic flow. This avoids wave drag and keeps nose ...


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